The Study of the Structural Colouration Observed in the Papilio crino Fabricius, 1792 Wings

Abstract

The research on nano-photonics has been on the increase recently. Among the materials that exhibit stunning optical properties are the nano-photonic materials found in nature such as those on butterfly wings. The wing scales of papilio crino was analysed using the Scanning Electron Microscopy (SEM), UV-Vis-NIR spectrometer, and Optical Microscopy (OPM). Under the OPM, the wing scales was imaged both in normal and polarized (45°) light. The SEM images reveal concave surfaces separated by repeating pattern of ridges and cross ribs. The variation in colour across the concave surface modulation was evident from the optical microscopy images. Through the numerical simulation and CIELab colour space, it was shown that the green colour seen on the wings is a combination of yellow and blue light reflected from different microscopic regions on the wing concave surface. This shows application in the bio-mimicks of retroflection sensors for the detection and classification of optical systems.